wire up chef handlers directly from librarieslcg/better-handler-wiring

smear just a little bit of minimal DSL wiring into the Chef::Report
class so that classes can wire themselves up automatically as
handlers.

this also extends the Chef::Config[*_handler] arrays to take classes
as well as instances.

in the case of passing a class that is not a singleton, a new instance
will be created when the report is run.  it will obviously be difficult
to pass any state into this instance.

if the class that is passed supports calling `#instance` we assume it
is a Singleton and get the instance and use that.  this is to support
other chef code grabbing/creating the singleton instance and poking
it with data (probably configuring where the reporter goes and what
creds it needs to publish and other stuff).

2 files changed, 120 insertions, 0 deletions

diff --git a/lib/chef/handler.rb b/lib/chef/handler.rb
index b720a11a45..100ed23d9e 100644
--- a/lib/chef/handler.rb
+++ b/lib/chef/handler.rb
@@ -57,16 +57,47 @@ class Chef
   #
   class Handler
 
+    def self.handler_for(*args)
+      if args.include?(:start)
+        Chef::Config[:start_handlers] ||= []
+        Chef::Config[:start_handlers] |= [self]
+      end
+      if args.include?(:report)
+        Chef::Config[:report_handlers] ||= []
+        Chef::Config[:report_handlers] |= [self]
+      end
+      if args.include?(:exception)
+        Chef::Config[:exception_handlers] ||= []
+        Chef::Config[:exception_handlers] |= [self]
+      end
+    end
+
     # The list of currently configured start handlers
     def self.start_handlers
       Array(Chef::Config[:start_handlers])
     end
 
+    def self.resolve_handler_instance(handler)
+      if handler.is_a?(Class)
+        if handler.respond_to?(:instance)
+          # support retrieving a Singleton reporting object
+          handler.instance
+        else
+          # just a class with no way to insert data
+          handler.new
+        end
+      else
+        # the Chef::Config array contains an instance, not a class
+        handler
+      end
+    end
+
     # Run the start handlers. This will usually be called by a notification
     # from Chef::Client
     def self.run_start_handlers(run_status)
       Chef::Log.info("Running start handlers")
       start_handlers.each do |handler|
+        handler = resolve_handler_instance(handler)
         handler.run_report_safely(run_status)
       end
       Chef::Log.info("Start handlers complete.")
@@ -90,6 +121,7 @@ class Chef
       events.handlers_start(report_handlers.size)
       Chef::Log.info("Running report handlers")
       report_handlers.each do |handler|
+        handler = resolve_handler_instance(handler)
         handler.run_report_safely(run_status)
         events.handler_executed(handler)
       end
@@ -115,6 +147,7 @@ class Chef
       events.handlers_start(exception_handlers.size)
       Chef::Log.error("Running exception handlers")
       exception_handlers.each do |handler|
+        handler = resolve_handler_instance(handler)
         handler.run_report_safely(run_status)
         events.handler_executed(handler)
       end
diff --git a/spec/unit/handler_spec.rb b/spec/unit/handler_spec.rb
index 65c3ddc4cb..a56645fa78 100644
--- a/spec/unit/handler_spec.rb
+++ b/spec/unit/handler_spec.rb
@@ -212,4 +212,91 @@ describe Chef::Handler do
     end
   end
 
+  describe "library report handler" do
+    before do
+      # we need to lazily declare this after we have reset Chef::Config in the default rspec before handler
+      class MyTestHandler < Chef::Handler
+        handler_for :report, :exception, :start
+
+        class << self
+          attr_accessor :ran_report
+        end
+
+        def report
+          self.class.ran_report = true
+        end
+      end
+    end
+
+    it "gets added to Chef::Config[:report_handlers]" do
+      expect(Chef::Config[:report_handlers].include?(MyTestHandler)).to be true
+    end
+
+    it "gets added to Chef::Config[:exception_handlers]" do
+      expect(Chef::Config[:exception_handlers].include?(MyTestHandler)).to be true
+    end
+
+    it "gets added to Chef::Config[:start_handlers]" do
+      expect(Chef::Config[:start_handlers].include?(MyTestHandler)).to be true
+    end
+
+    it "runs the report handler" do
+      Chef::Handler.run_report_handlers(@run_status)
+      expect(MyTestHandler.ran_report).to be true
+    end
+
+    it "runs the exception handler" do
+      Chef::Handler.run_exception_handlers(@run_status)
+      expect(MyTestHandler.ran_report).to be true
+    end
+
+    it "runs the start handler" do
+      Chef::Handler.run_start_handlers(@run_status)
+      expect(MyTestHandler.ran_report).to be true
+    end
+  end
+
+  describe "library singleton report handler" do
+    before do
+      # we need to lazily declare this after we have reset Chef::Config in the default rspec before handler
+      class MyTestHandler < Chef::Handler
+        handler_for :report, :exception, :start
+
+        include Singleton
+
+        attr_accessor :ran_report
+
+        def report
+          self.ran_report = true
+        end
+      end
+    end
+
+    it "gets added to Chef::Config[:report_handlers]" do
+      expect(Chef::Config[:report_handlers].include?(MyTestHandler)).to be true
+    end
+
+    it "gets added to Chef::Config[:exception_handlers]" do
+      expect(Chef::Config[:exception_handlers].include?(MyTestHandler)).to be true
+    end
+
+    it "gets added to Chef::Config[:start_handlers]" do
+      expect(Chef::Config[:start_handlers].include?(MyTestHandler)).to be true
+    end
+
+    it "runs the report handler" do
+      Chef::Handler.run_report_handlers(@run_status)
+      expect(MyTestHandler.instance.ran_report).to be true
+    end
+
+    it "runs the exception handler" do
+      Chef::Handler.run_exception_handlers(@run_status)
+      expect(MyTestHandler.instance.ran_report).to be true
+    end
+
+    it "runs the start handler" do
+      Chef::Handler.run_start_handlers(@run_status)
+      expect(MyTestHandler.instance.ran_report).to be true
+    end
+  end
 end